题目描述
Victoria has a tree, $\mathbf{T}$, consisting of $N$ nodes numbered from $1$ to $N$. Each edge from node $U_i$ to $V_i$ in tree $\mathbf{T}$ has an integer weight, $W_i$.
Let's define the cost, $\mbox{C}$, of a path from some node $\mbox{X}$ to some other node $\mathbf{Y}$ as the maximum weight ($\mbox{w}$) for any edge in the unique path from node $\mbox{X}$ to node $\mathbf{Y}$.
Victoria wants your help processing $Q$ queries on tree $\mathbf{T}$, where each query contains $2$ integers, $\boldsymbol{\mbox{L}}$ and $\mbox{R}$, such that $L\leq R$. For each query, she wants to print the number of different paths in $\mathbf{T}$ that have a cost, $\mbox{C}$, in the inclusive range $[L,R]$.
It should be noted that path from some node $\mbox{X}$ to some other node $\mathbf{Y}$ is considered same as path from node $\mathbf{Y}$ to $\mbox{X}$ i.e $\{X,Y\}$ is same as $\{Y,X\}$.
Input Format
The first line contains $2$ space-separated integers, $N$ (the number of nodes) and $Q$ (the number of queries), respectively.
Each of the $N-1$ subsequent lines contain $3$ space-separated integers, $\mbox{U}$, $\mbox{V}$, and $\mbox{w}$, respectively, describing a bidirectional road between nodes $\mbox{U}$ and $\mbox{V}$ which has weight $\mbox{w}$.
The $Q$ subsequent lines each contain $2$ space-separated integers denoting $\boldsymbol{\mbox{L}}$ and $\mbox{R}$.
Constraints
$1\leq N,Q\leq10^5$
$1\leq U,V\leq N$
$1\leq W\leq10^9$
$1\leq L\leq R\leq10^9$
Scoring
$1\leq N,Q\leq10^3$ for $30\%$ of the test data.
$1\leq N,Q\leq10^5$ for $\textbf{100\%}$ of the test data.
Output Format
For each of the $Q$ queries, print the number of paths in $\mathbf{T}$ having cost $\mbox{C}$ in the inclusive range $[L,R]$ on a new line.
Sample Input
5 5
1 2 3
1 4 2
2 5 6
3 4 1
1 1
1 2
2 3
2 5
1 6
Sample Output
1
3
5
5
10
Explanation
$Q_1$: $\{3,4\}$
$Q_2$: $\{1,3\},\{3,4\},\{1,4\}$
$Q_3$: $\{1,4\},\{1,2\},\{2,4\},\{1,3\},\{2,3\}$
$Q_4$: $\{1,4\},\{1,2\},\{2,4\},\{1,3\},\{2,3\}$
...etc.
输入格式
见题面
输出格式
见题面